Treating hydrocarbon oils



Sept. 7, 1943. H. WALKER TREATING'` HYDROCARBON OILS Filed July 12, 1941 HARRY H.WALKR IN VEN TOR (jj/w HIS TTORNE YS (IP-lic M300 Patented Sept. 7, 1943 Y iiJNl'l-EDA STATES ix'iENT OFFICE f .v` QZSZSVGQM ,v y t d TaEATING HYDROOARBON oILs y Harry,` Il. rvWalker, Lockport, Ill.; Aassignor, yby

mesne assignments, to rThe Texas Company, NewYork, N. Y., a corporation. of Delaware Application July 12, 1941, serial No. 402,233

' 5 claims. (o1. 19e- 33) ,t This invention relates to a processof treating l hydrocarbon oils, particularly` `petroleum oils, which results in freeing the oils of objectionable sulfur compounds such as mercaptans, which impart an undesirable odor to the oils.

The invention especially relates to an improved `method of carrying out the so-called doctor treatment of sourY hydrocarbon 1 oils. In this treatment an alkaline solution of alkalimetal plumbite, the doctor solution, is employed for contacting the-sour oil, the solution usually being prepared by dissolvinglitharge in an aqueous `solu- 1 tion of causticsoda'. The treatment also usually comprises adding sulfur to the sourhydroc'arbon oil, the sulfur being added either before or after the admixture of the sourcil with the doctor` solution. In some cases the partially spent doctor may be removed from the oil prior to the addition of sulfur. Although it is now generally recognized that a number ofside reaction occur simultaneously, the three main-reactions` con- "sidered to take place in this treatment are as In the above equations the letter R represents the hydrocarbon radical of a mercaptan present in thesour oil. f

separate suspended impurities from hydrocarbon oils. For example, the' invention! .can be appliedto the separation of suspendedlead sulfide from gasoline treated by a process in which an alkalinesolutionfof lead sulfide is used.` L

It has been discoveredin accordancewith the invention 'that byinjecting steam intov a flow'- ing stream oi a hydrocarbon oil, suchas. gasoline or kerosene, following the doctor treatment 'oftheoil which oil therefore contains suspended lead sulfide and other impurities, the settling of these impurities is accelerated and made` more complete. Assa resultthe time of settling and equipment required'therefor are reduced and the necessity for washing with water is eliminated.

To illustrate one manner in which the present invention maybe applied, a conventional doctor The final products of the treatment as shown `by Equation'Sl are' Adisulrldes vand lead sulfide.` The disulfldes areoil-s'oluble, odorless compounds,

`usually necessitated a large]quantityL oi settling space. Also, -it has been` .customary to subject the oil containing" the lead sulideltoja "washing with water,A a time-consuming 'operation requiring a settling period. f

The present invention is concerned with an imagain provement which resultsin substantial increase inthe rate Vandiefli'ciency of the separation of suspended vrimpurities, particularly lead sulfide, from a doctor-:treated oil. Itis also believed-that the improvementmay ybe employed with advantage-in othersituationswhere it is desired to` sulfide. .one or more settlers, which are usually enlarged treatingprocess will be described It will be understood that the invention may also be applied to otherA doctor treating processes which result in the production of a hydrocarbon oil containing suspended'lead suliide and other impurities. In the process in question, thesour oil is mixed with doctor solution byintroducing the solution into a stream ofthe oil and then passing, the combined materials through a conventional mixer. Sulfur, preferably in solution in oil, is then introduced `in amount sufficient toconvert the lead 'mercaptides,`form"ed by reaction ofniercap.- tans withsodium plumbite, to disuldes and `lead The resulting oil is then flowed through chambers equippedwithmeans for removingr materials from the bottom and an overflow con- `nection for.` carrying the oil, to remove .excess doctor andthe more easilyprecipitated leadsul- `fide and other impurities. The partially treated oil is then owed in aconned stream to one lor more nal settlers, one or two plus a run-down Vtank usually being employed. It has been` prior 'practice to subject the oil to a waterrwash prior to this introduction into the final settlers. This has required arelatively large quantity ofwater Aand 'alsohas caused a slowing-up of the operation in *order to separate thel water and obtain an oilv ofsatisfactory color.

`:In applying the present invention to" the system just described, the water wash is eliminated 'and While passing theconiined stream of'oil` to the nalsettlers there is introduced a small amount of steam; This modiiied `process is i1- lustrated in the accompanying drawing, which o thefoil after the the present improvement is applied will not n differ substantially from the conditions usually maintained. For example',

may vary from about 60 F. to 85 "F, but in order to avoid emulsion difculties it is generally pre-.

ferred to operate Within the range of 70 110.85 F. The pressure maintained during .the operation will' normally vary from atmospheric to about. 151 pounds gauge.4 In, doctor treating sour naphthas in the majority of reneries the: ria-phtha charge vrate will Vary from 250 to 4G@y barrels per hour. As pointed out above,4 steam is introduced into. a confined stream of the oil passing to the fina-l settlers. At a 'chargeprate' Within the above' range, this streamy m'ay be carried by :a line Varying from abouttwo inches .to about six inches in internal diameten. and, williusually have an internal diameter of three-to fou-rinches. o

Under these conditions thesteam may" be introduced through a one-fourth inch to orreehalf inch line, and saturated live steam is ordinarily employed `at a pressure :above 160- pounds per square inch. Only enough steam is employed to eiect complete dispersion of fine particles of Water, since when using. steam excess no improvement in settling 'is noticed. It hasfbeen found that at na-phtha charge rates as. high 'as 400' barrels per .hour'na steam'` charge of two ypounds per minutewill accomplish Ythey desired result and it may be sta-ted.- that under these conditions a.- steam charge' rateiof greater than about three poundsI per minute Will be'unneceslsary.

In one operation of theprocess gasour. naphtha charge-rate of.330barrels iper` hourpW-a'sf mairitained' and after completion ofA the doctor Ytreat'- ment and preliminary settling,v saturated.- live` steam'V at 114i) pcundsper square inch, approximately 95% quality, .was introduced through a one-fourth inch line, the steam injection being `at the rate of not more thanl one-half-pound per barreloi` naphtha charged; Iln this casethe .temperature was maintained' at; abouti" F; and the pressure from atmospheric? pressure to y1'5 pounds gauge. Asa result of the steam injection, the suspended lead sulfide appeared to coalesce so that' an. efficient 'separation was accomplished in the following settlersftoyield a finished gasoline-oi good colo-r; i

When employing steam as describedy herein the rise in temperature of the confined# stream.` of hydrocarbon oil is relatively small; for example, it rarely exceeds one or,tWo -degrees.V In certain eases, particularly where'the initial temperature ot the oil is low, aV greater rise in temperature,

lfory example, a rise of ll to 156 Flmightresult from .the steam injection. y

Thereason Why the injection of steamZ functions in the manner described isnot clearly: un-

derstood land it is-` therefore not intended. toll-mit `the.invention-1toa-ny theory of operation-. However,- it may be: of advantage to; point -out .that

as usually practiced the injection of steamtakes in 'treating' sourY naphtha the Itemperature of the' charge stock place at a point in the system where the reac tion is considered to have gone to completion rand therefore the steam injection does not aid the actual chemical reaction taking place. Also, it appears that agitation' alone is not the result of the injection because other kinds of agitation do not produce comparable results. One possible explanation is `that the steam becomes dispersed in the naphtha in the form of small globules of Water and, because of the greatl absorptive surface per unit quantity of Water, is able to entrain suspended particles and cause their rapid precipitation and settling. There is also a possibilitythat `the finely-dispersed Water globules havelan; effect upen the electrical charge of the suspended particles of lead sulde and by altering that charge increase the tendency of the v lead sulfide particles to coalesceand form larger particleswhich settle rapidly.

The present invention is particularly important because of thev continually growing understa-nding that in the doctor treatment of: sour naphtha the use ot an excess of. sulfur should be avoided in order not to `decrease the octanenumber or tetra-ethyl. lead susceptibility ot the finished gasoline. Where an excess ofY sulfur isV usedsettling diiculties are reduced, but where only the amount of sulfur theoretically 4required is used,. the `leadv .sulfide is iorrned as nelydiity separation of. lead sulfide sludge, the method l Kof improving the settling of said sludge which comprises introducing steam into said confined stream of' Oil and' passingy the" resulting stream into said settling. vessel.

2. In' the process of sweetening a petroleum oil'- comprising treating an oil containing sulfur compounds with an alkaline solutionV ofalead compoundA to produce an oil substantially free from odorif'erous sulfur compounds butcontain ing suspended lead sulde,.. thelimproveme'nt which comprises injecting, steam in'tofafcon'ned flowing stream of the oil to increase tl'ie tenden-` cy of the suspended lead sulfide to' precipitate, permitting the oill -to settler and separati'rigpiecipitated lead slllde from the oil.

3. In the process of sw'eetering asourn'apltlfi'a comprising mixing the, naplitha With an alkaline solution 0I" SOdillll pliljnb'it,. aIidlS' 'Irliiirig tlie naphtha with an ramount of sulfur at least s'uit` ycientlto react with theV lead' mercapti'des formed bythe reaction of the mercaptaiis in said sour naphth'a With Said' sodium plu-Inbite, the improvement which comprises settling. the' naplitha after the addition of the alkaline solution. of

and the easily, precipitatedrlead suldeiormed in the reaction, leaving anaphtha containing Vsus-` pended lead sullde,` injecting.` steam.. into" a confined flowing stream of said naphtha containf ing suspended lead sulfide to increase the tendency of said suspended lead sulfide to precipitate, and separating precipitated lead sulde from the n'aphtha.

4. In the process of sweetening a sour naphtha comprising mixing the naphtha with an alkaline solution of sodium plumbite, and also mixing the naphtha with an Iamount of sulfur su'cient to react with the lead mercaptides formed by the reaction `of the mercaptans in said sour naphtha With said sodium plumbite, the improvement which comprises settling the naphtha after addition of the alkaline solution of sodium plumbite and the sulfur to remove any excess of alkaline solution of sodium plumbite and the easily precipitated lead sulfide formed in the reaction, leaving a naphtha containing suspended *lead sull-1de, injecting steam into a confined owing stream of said n'aphtha containing suspended lead sulfide to increase the tendency of said suspended lead sulde to precipitate, the steam being injected in an amount corresponding to about one-half pound of steam for eachvbarrel of naphtha, and separating precipitated lead sulfide from the naphtha.

5. In the process of sweetenng a sour naphtha comprising mixing the n-aphtha Withan lalkaline solution of sodium plumbite, and also mixing the naphtha with an amount of sulfur suiicient to react with the lead mercaptides formed by the reaction of the mercaptans in said sour naphtha with said sodium plumbite, the improvement which comprises settling the naphtha after addition oi the alkaline solution of sodium plume bite and the sulfur to remove any excess `of alkaline solution of sodium plumbite fand the easily precipitated lead sulde formed in the reaction, leaving a naphtha containing suspended lea'd sulde, flowing said naphtha containing suspended lead sulfide in a conned stream, injecting steam into said confined stream to increase the tendency of the suspended lead sulfide to precipitate,'the amount of steam injected corresponding to not more than three pounds per minute through a line having an internal diameter of about one-fourth to one-half inch for a n'aphtha iioW of about 250 to 400 barrels per hour through a line having an internal diameter of about two to six inches, and separating precipitated lead sulde from the naphth-a- HARRY H. WALKER. 

